A xenobiotic (Greek, xenos "foreign"; bios "life") is a compound that is foreign to a living organism. Principal xenobiotics include: drugs, carcinogens and various compounds that have been introduced into the environment by artificial means.

A drug used to prevent nausea or vomiting. An antiemetic may act by a wide range of mechanisms: it might affect the medullary control centres (the vomiting centre and the chemoreceptive trigger zone) or affect the peripheral receptors.